Halep did very to hold serve in the very first game of the 3rd set, despite facing two break points and used this momentum to go up 3-1 in the deciding set. But, similar to Roger Federer against Rafael Nadal in this year's Australian Open men's final, Ostapenko negated the score by holding her own serve and creating relentless pressure in her service return games and ended up winning the last 5 games to win the match 4-6 6-4 6-3. The pivotal point was at 3-all in the 3rd set with Halep serving and facing breakpoint when Ostapenko hit a backhand down the line that was going a foot wide but hit the net and bounced high and onto Halep's side of the net for a winner to earn the break. That was basically the coup de grace because then Ostapenko was able to hold serve to go up 5-3 and basically picked on Halep's weak serve return in the final game, ending with a down-the-line backhand service return winners on match point.
With the win Ostapenko will rise from #47 to #12 in the world. She is a former Junior Wimbledon champion and should be expected to have even better results on faster surfaces like grass and hard courts. Halep rises to #2 in the rankings and Angelique Kerber who lost on the very first day of play of Roland Garros 2017 will remain #1 the day after it.